1. Field of the Invention
This invention relates to a process for insulating a wall under construction, and more particularly the invention relates to a process for installing loose-fill insulation in a partially enclosed wall cavity.
2. Brief Description of the Prior Art
Loose-fill insulation blown into ceilings and outside wall cavities is very effective in reducing heat transfer in existing buildings. Exterior walls can be reinsulated without removing the interior surface, access to wall cavities being provided by bored holes in exterior siding, or the like. In addition, loose-fill blown insulation can be used in new construction, where insulative batts are often used.
Loose-fill insulation can provide a substantial advantage over batt-type insulation in that the loose-fill material readily assumes the actual shape of the interior cavity being filled, whereas the insulative batts are manufactured in a limited number of standard size widths, none of which will as closely match the actual dimensions of wall cavities encountered in the field. The principle advantage of insulative batts lies in the rapidity with which they can be installed. Installation of loose-fill insulation in walls containing obstructions is as rapid as installation in otherwise empty walls. The loose-fill insulation, properly installed, fills the complete wall cavity, conforming to the actual shape of the wall cavity and providing, in that respect, effective resistance to heat transfer through the wall. Loose-fill insulation also lends itself to installation in ceilings, party walls and essentialy any other place where it is desired to resist heat transfer, as an alternative to batts, especially where there are obstructions such as, water, waste and gas lines, electrical conduits, heating and air conditioning ducts, etc.
In general, when an exterior wall is to be insulated, a vapor barrier is placed between the insulation and the interior surface of the exterior wall, and the exterior surface of the exterior wall is allowed to "breathe" so that adventitious water vapor will not be trapped within the wall. On the other hand, exterior wall sheathing is itself sometimes backed with sheet insulation. For example, aluminum siding is available with polystyrene sheet backing. The sheet insulation provides some measure of protection to the exterior wall on which the sheathing is applied. However, it is also desirable to fill the wall cavity with insulation to further reduce the rate at which heat is transferred through the wall. In this case, a vapor barrier between the insulation in the wall cavity and the interior surface of the wall should not be used, because the insulative sheet in the sheathing itself serves as a vapor barrier. A second barrier would trap moisture within the wall cavity, possibly causing serious damage to the structure.
Prior art methods of insulating new construction with loose-fill insulation preumatically injected or blown into wall cavities require that a retaining sheet, such as a vapor barrier film, screen, etc. be secured on the inside of the wall before insulation is blown into the wall cavity. The retaining sheet prevents loose-fill insulation from falling from the wall cavity before the interior surface of the wall, typically gypsum wall board or the like, is added to enclose the wall cavity. Yet a vapor barrier film should not be used when the exterior surface of the wall itself includes a vapor barrier. Further, the installation of the vapor barrier film is an additional labor-intensive step which increases the cost of construction. Clearly, there is a need for a process for installing loose-fill insulation in new construction without the necessity of fitting a vapor barrier film or the like on the interior surface of the wall before blowing insulation into the wall cavity.